Organic Light-Emitting Diode (OLED) has the advantages of simple process, low cost, capable of adjusting color of the emitted light in the visible region, easy for mass production, good flexibility and the like, and thus an OLED display device using the OLED is regarded as one of the most promising display technologies in the future. White OLED (WOLED) has a power efficiency over 60 lm/W and a lifetime of 20,000 hours or more, which greatly promotes the development of the WOLED display device.
FIG. 1(a) is a schematic diagram illustrating a conventional WOLED without a microcavity structure. As illustrated in FIG. 1(a), the WOLED adopts an organic light-emitting layer 102 formed by light-emitting materials of three primary colors of red, green and blue, so that the organic light-emitting layer 102 emits white light. The organic light-emitting layer 102 is disposed between a cathode 101 and an anode 103, and the white light emitted from the light-emitting layer 102 exits on the anode side after reflected by the cathode 101.
In order to improve light extraction efficiency of the WOLED and increase brightness of the WOLED display device, a transflective layer 103′ is provided on the anode side, so as to form a microcavity structure between the cathode 101 and the transflective layer 103′, as shown in FIG. 1(b). The microcavity structure is a structure with a thickness of micrometers formed between the reflecting layer and the transflective layer. The microcavity structure enhances the intensity of light based on the following principle. Light from the light-emitting layer is repeatedly reflected between the reflecting layer and the transflective layer, light with particular wavelength among the light ultimately emitted from the transflective layer will be enhanced due to the resonance effect, and the wavelength of the enhanced light is relevant to the thickness of the microcavity. In the WOLED display device, different pixel units are used to emit light of different colors, thus the microcavities in different pixel units should have different thicknesses so that light of different wavelengths can be enhanced in the different pixel units.
FIG. 2 is a structural schematic diagram illustrating an array substrate of the conventional WOLED display device with the microcavity structure, and FIG. 3 is a structural schematic diagram illustrating another array substrate of the conventional WOLED display device with the microcavity structure. As shown in FIGS. 2 and 3, a color filter film is disposed outside the microcavity structure, color filter films of different colors belong to different pixel units, and microcavity structures corresponding to the color filter films of different colors have different thicknesses.
FIG. 4 is a schematic diagram illustrating a comparison between a brightness of a WOLED with the microcavity structure and a brightness of a WOLED without the microcavity structure, wherein the dotted line corresponds to the brightness of the WOLED without the microcavity structure, and the solid line corresponds to the brightness of the WOLED with the microcavity structure. As illustrated in FIG. 4, by using the microcavity structure, the brightness of the blue light is increased by about 1.6 times, the brightness of the green light is increased by 2.5 times, and the brightness of the red light is increased by about 2.2 times.
Although the conventional microcavity structure enhances the intensity of the light, it can be seen from FIGS. 2 and 3 that the conventional microcavity structures have relatively complex hierarchy structures, it is required that the microcavity structures in the regions corresponding to the color filter films of different colors to have different thicknesses, and thus the fabrication process is relatively complex.